| 摘要 |
PURPOSE:To make the thickness of a set layer thinner from the lower part to the upper part thereof in the setting process and prevent a defect such as voids produced in the central part or the appearance of bubbles, by making the cross-sectional area of the upper part of a mold smaller than that of the lower part. CONSTITUTION:A mold 3 is made gradually thinner from the lower part to the upper part thereof. Accordingly, because the water-absorption capacity is decreased with the thinner mold, the setting speed is lower at the position nearer from the top of the mold. Consequently, the densities of molded items 1 and 2 are lower than usual in its surface, however, the ratio of decrease in density is less from the surface to the central part. That is to say, as a directional setting progresses, the area of a flowable liquid phase is larger at the upper part of the mold and as a mud is easily supplied, a defect such as small voids can be hardly produced in the center of the mold. |
